Neuromyelitis optica
NeuroMyelitis Optica (Devic's disease) Please look up Dr Kevin Tan lecture"Neuroimmunology" in the ONE-E-Archive The syndrome of neuromyelitis optica (NMO) is defined as the co-occurrence of optic neuritis with myelitis. This combination of neurological impairments occurs in patients with multiple sclerosis (MS), acute disseminated encephalomyelitis (ADEM), systemic lupus erythematosus (SLE), and Sjögren syndrome. NMO has been associated with several systemic diseases including collagen vascular diseases, autoantibody syndromes, infections, and toxic exposures. The clinical course of NMO is variable. It may occur as a monophasic illness that is either fulminant and fatal or associated with varying degrees of recovery. Polyphasic courses characterized by relapses and remissions also occur (like in the chinese lady we examined during Prof Umapathi's ward rounds). There is much debate as to whether NMO is a distinct disease, and what its relationship is to MS and other inflammatory disorders. Whether or not the NMO phenotype corresponds to a unique biologic process will await the identification of a disease-specific marker and, ultimately, the elucidation of the syndrome's pathogenesis. Epidemiology Rare, constituting less than 1% of demyelinating disease in Western countries. Men and women thought to be equally affected, although in more recent case series women are overrepresented. Age: Ranges from childhood to late adulthood, with the incidence apparently tapering off after the fifth decade. Pathogenesis NMO is similar to MS in that it is an autoimmune demyelinating disease. Unlike MS, the attacks are believed to be mediated by NMO-IgG antibodies.which target a protein called aquaporin 4 in the cell membrane of astrocytes which acts as a channel for the transport of water across the cell membrane. Aquaporin 4 is found in the processes of the astrocytes that surround the blood-brain barrier, which is weakened in NMO, but it is currently unknown how the NMO-IgG immune response leads to demyelination. Clinical Features Cases can present with either visual loss or myelopathy. Occasionally, optic nerve and spinal cord symptoms begin simultaneously. Either one or both eyes may be involved, and the extent of myelitis is variable. May be preceded by a prodrome of fever, myalgia, headache, or sore throat. Generally, NMO is sporadic, although there are a few case reports of familial occurrences. Some patients have a monophasic illness, especially in the pediatric population. Others have polyphasic illness characterized by relapses and remissions with variable degrees of recovery between episodes. The proportion of patients in each of these two groups varies depending on the criteria used to define NMO. In the pediatric population, NMO is frequently preceded by infection. Pediatric cases typically have a monophasic course and many have complete neurological recovery. Physical Examination Ophthalmoscopic examination may be normal or find signs of optic neuritis, or optic atrophy in chronic cases. Visual field testing typically reveals a central scotoma. Relative afferent pupillary dilation may be present, but can also be absent if both the optic nerves are affected equally. The spinal cord symptoms in NMO are not different from those of other causes of myelitis. Patients may suffer from painful tonic spasms. Cerebral and brainstem findings should not be present; if they are present, a search for alternative etiologies is warranted. Diagnostic Criteria Source Medscape review article